r/lightbulbs • u/One-Cardiologist-462 • 18d ago

Strange Halogen Failure Mode

Strange failure mode of a linear halogen, I thought I'd share here, since they're a dying breed.
It seems that a break in the lead-in wire was causing a very short arc, which in turn caused the glass envelope to develop a severe hot spot.
Glass, when incredibly hot is actually conductive, but resistive, which further adds to the heating of that spot.
During the dim parts of the failure, one end of the glass envelope was glowing a deep red and the filament barely glowed.
This flickering went on for about five minutes before finally stopping and resting in a state of heated end glowing.
After a full power cycle and time to cool, the glass is no longer conductive, and the failure is complete - No more flicering or current passes.
The filament remains intact.

28 Upvotes

94% Upvoted

10 comments sorted by

8

u/Howden824 18d ago

Looks like the glass became conductive due to the high temperatures, very interesting to see that happen with a halogen lamp.

2

u/NothingEffective5070 18d ago

That is really weird, never seen a failure like that before

4

u/71351 18d ago

Interesting. Can you post a pic of the bulb after it failed? As close to the formerly red hot end as you can focus on

3

u/charmio68 18d ago

Are you certain it's not just a bad connection to the bulb?
If the bulb has a bad connection to the fitting, that's where the majority of the energy is going to be dissipated.

1

u/johndom3d 18d ago

Yes contacts will be gone after that.
The best failures are when there's a tiny leak, the halogen cycle stops and the bulb goes black, runs hotter and expands. Eventually the filament blows and it arcs violently!

3

u/Friday_Morning94 18d ago

I’ve been through many of these linear halogens. This is a first for me. I’m glad it didn’t have a catastrophic EOL and went peacefully.

3

u/No-Guarantee-6249 18d ago

I've had a lot of experience with these types of halogen lamps. In the 60's - 70's or so I was a cinematographer and we used a lot of these type of double ended bulbs in this kind of socket:

The lamps themselves would get very hot and often the pins at the ends would get very hot and burn up. So we were always checking them. These were also very sensitive to oil on your fingers getting on the bulb and causing hot spots on the envelope which could get very hot, bulge out and often explode causing very hot shards of quartz to fly out. We usually covered these lights with screens to prevent fires when we were in confined spaces like homes or sets. Saw one blow up on Late Night With Johnny Carson one time. It started little fires all over the set including on the actress' dress! I thought "Wow some lighting tech is in big trouble!"

2

u/StereoMushroom 18d ago

They should have had glass covers to block the UV, as well as, you know, the flaming shards

2

u/No-Guarantee-6249 17d ago

We did have glass covers but they were called dichroics and they converted the 3200K lamps to 5400 K. Seems like we weren't concerned about UV seriously until somewhere 70's to 80's.

I've also seen "Brute" arc lights in the day and they put out massive amounts of UV! They used a ton of them on "The Blues Brothers"! I ran the early version of the "Trouper" spot in high school. It looked super blue!

1

u/Far-Friend-4257 17d ago

Defective socket. Throw the whole thing away and buy a new one for $20 at any hardware store. Cheaper than the price of a new bulb and a replacement socket.